Ground state and properties of ferroelectric superlattices based on crystals of the perovskite family |
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Authors: | A I Lebedev |
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Institution: | Institut für Theoretische Physik, Universitaet Regensburg, 93040 Regensburg, Germany |
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Abstract: | The crystal structure of the ground state of ten free-standing ferroelectric superlattices based on crystals with the perovskite
structure (BaTiO3/SrTiO3, PbTiO3/SrTiO3, PbTiO3/PbZrO3, SrZrO3/SrTiO3, PbZrO3/BaZrO3, BaTiO3/BaZrO3, PbTiO3/BaTiO3, BaTiO3/CaTiO3, KNbO3/KTaO3, and KNbO3/NaNbO3) was calculated from first principles within the density functional theory taking into account criteria for stability of
the structures with respect to acoustic and optical distortions. It was shown that the ground state in all the considered
superlattices corresponds to the ferroelectric phase. It was found that the polarization vector has a tendency toward a tilt
to the plane of the superlattice layers, which makes it possible to decrease the electrostatic and elastic energy in the superlattices
consisting of materials with different ferroelectric properties. The importance of the inclusion of structural distortions
due to unstable phonons at the Brillouin zone boundary, which, in a number of cases, lead to significant changes in ferroelectric
and dielectric properties of the superlattices, was demonstrated. |
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